1. Field of the Invention
The present invention relates to a manufacturing method for a three-dimensional structural body which is used as an optical waveguide, an optical resonator, a near-field optical probe, a birefrigent element, a filter, a branching element, a wavefront converter or a polarizer in the field of optical communication, optical interconnection, optoelectronics, or optical measurement and includes a diffraction-type optical element, a multilayer film having a periodic structure, a photonic crystal and the like.
2. Description of the Related Art
It is conventionally known that a medium in which the distribution of refractivity has a periodic structure with a pitch nearly equal to the wavelength of light, has a unique light propagation characteristic. As a medium having a one-dimensional periodic structure, a dielectric multilayer film is known for a long time, and its design theory and manufacturing technique are already in a mature field.
On the other hand, a method for controlling spontaneous emission in a semiconductor element by using a medium having a three-dimensional periodic structure with a pitch nearly equal to the wavelength of light was proposed in 1987 by E. Yablonovitch, Phys. Rev. Lett., vol. 58, (1987), P2059-P2062, and since then, attention has been paid to the behavior of light in a two-dimensional or three-dimensional periodic structural medium.
In such a medium, the propagation of light having a wave vector in a specific range is inhibited, and a photonic band similar to an energy band of an electron in a semiconductor is formed. A periodic refractivity structure forming the photonic band is called a photonic crystal.
When the photonic band is used, novel control of a photon becomes possible, and therefore, various applications are expected. There are already proposed applications to a laser having a low threshold or no threshold by control of spontaneous emission light (Baba et al., Applied Physics, vol. 67, (1988), P1041-P1045), an optical waveguide using a property that light localizes around a lattice defect in a photonic crystal (J. D. Joannopoulos et al., Photonic Crystal, Princeton University Press, (1995 Princeton, N.J.), P100-P104), a microminiature optical resonator using the localization of light and having high efficiency and the order of μm (Baba et al., Applied Physics, vol. 67, (1988), P1041-P1045), an element having a new prism function in which a deflection angle is greatly changed by a very small change of a wavelength or an incident angle (Kosaka et. al., 59th Japan Society of Applied Physics Lecture Meeting Collected Preprint (Ouyou Butsuri Gakkai Gakujutsu Kouenkai Yokoushu) III, 17p-T-13, (1998), P920), and the like.
Although the individual elements of these optical elements have various optical functions such as emission control of light, propagation control, prism function, filter function, and optical waveguide, when they are further combined with a light emitting element and a light receiving element, various electronic functions and optical functions appear.
In the photonic crystal, a three-dimensional photonic crystal is most desirable as a structure in which a photonic band effect is obtained most. Besides, in the three-dimensional photonic crystal, a structure is desirable in which a complete photonic band gap can be obtained, and a defect can be inserted relatively easily and freely into the three-dimensional photonic crystal. However, there are relatively few fabrication methods for the three-dimensional photonic crystal as described above in which the complete photonic band gap can be obtained and the defect can be freely inserted, and its fabrication is very difficult. As a conventional fabrication technique which can obtain such a complete photonic band gap and can freely insert a defect into the three-dimensional photonic crystal, for example, there is a fabrication method (first method) disclosed in Directed by Shoujiro Kawakami, Photonic Crystal Technique and Its Application, CMC Publication, Chapter 11, 2002 or APPLIED PHYSICS LETTERS VOLUME 81, NUMBER 17, pp 3122-3124, 2002.
In this method, a two-dimensional microplate with an air bridge structure fabricated using a semiconductor micromachining process and an undercut etching is previously fabricated on a substrate, the microplate is separated from the substrate by a micro-manipulator, the microplate separated from the substrate is subjected to adsorption, transfer, and position fine adjustment by the micro-manipulator again and is laminated. This process is repeated to perform laminating, so that the three-dimensional photonic crystal is fabricated.
As another method (second method) for manufacturing a three-dimensional periodic structural body, there is a method of repeating a process in which a slice pattern of the three-dimensional periodic structural body is formed on a support substrate, and another substrate (target substrate) is pressed against the slice pattern from above to perform transfer (JP-A-2001-160654, Japanese Patent No. 3161362).
However, in the first method, although it is possible to freely introduce the defect, since the micro-manipulation is used, many steps are required for one structure of the microplate subjected to the micromachining and constituting the photonic crystal. Thus, for the fabrication of the three-dimensional photonic crystal, it is necessary to perform the steps several times equal to the number of times of lamination, and a long time and a large number of steps are required for the fabrication of one photonic crystal. Further, when the manipulator is brought close to the individually cut cross-sectional form members, the respective members are attracted by or repelled from the manipulator by the interaction such as electrostatic force, intermolecular force, or magnetic force, so that the arrangements and directions become irregular, and much labor is required to adjust and laminate these, which is not efficient.
Besides, in the second method, in order to ensure the transfer of the slice pattern from the support substrate to the target substrate, it is desirable to form a peeling layer between the slice pattern and the support substrate. However, the combination of the material functioning as the peeling layer and the material enabling film formation on the peeling layer is limited, and there is a problem that the selection of materials constituting the three-dimensional periodic structural body is limited.
For example, although a laser or an LED using the photonic crystal is proposed, in the case where such an active element is formed of the photonic crystal, a semiconductor material is desired as a material constituting this, and the crystallinity of the semiconductor material greatly influences the characteristic of the laser or the LED. However, in the case where resin such as polyimide is used as the peeling layer, it becomes difficult to forma semiconductor film having high crystallinity on the layer, so that it becomes difficult to efficiently manufacture the photonic crystal containing the high crystallinity semiconductor as its construction material.